THIRTY-FIFTH ANNUAL CONVENTION. 263 



feet in diameter and 30 feet deep will contain 119 tons of silage, 

 while if its depth be 40 feet, it will contain 180 tons, or one- 

 half more. 



The Animal Husbandry Section has furnished the following 

 table in regard to the approximate amount of silage required 

 per day for various kinds of stock. 



The preceding table in connection with Table I, may be used 

 to determine the size of silo needed to fulfill various conditions. 

 For instance, if the silage is to be fed to a herd of forty dairy 

 cattle at the rate of 40 pounds per head per day, a silo 16 or 

 18 feet in diameter will be satisfactory. 



The Design of Silos. 



In the Eighth Annual Report of the Wisconsin Agricultural 

 Experiment Station, Professor F. H. King gives the results 

 of investigations to determine the pressure of silage against 

 the silo wall. It was found in these experiments that the 

 pressure of silage upon the silo wall increased with the depth 

 and was equal to 11 pounds per square foot of each foot of 

 depth. Thus at a depth of 20 feet, the bursting pressure in a 

 silo is 220 pounds per square foot, and at a depth of 35 feet 

 the pressure would amount to 385 pounds. A careful investi- 

 gation of modern practice has proven that an allowance for 

 this pressure is sufficient. As the cost of steel hoops or rein- 

 forcement to provide for this pressure is not excessive, fur- 

 ther work along this line does not seem to be necessary. In 

 an investigation of several failures of hoops of stave silos, it 

 was found in each case, that their rupture was due to excessive 

 swelling of the staves or to faulty material or workmanship in 

 threading the ends of the hoops. 



In stone, brick and concrete silos, there is, however, some 

 doubt as to whether it is necessary to provide enough steel to 

 carry the entire bursting pressure of the silage. Many con- 

 crete silos are now standing and in successful service with much 

 less reinforcement than that required by an assumed pressure 

 of eleven pounds per square foot per foot of depth. This is 



